The present invention relates to a method and an apparatus for immunoassay utilizing the reaction between an antigen and an antibody, and more particularly to an analyzing method and an analyzer in which magnetic particles are used as the solid phase for an immunoreaction.
The immunoreaction forming an immunocomplex is employed to determine antigens and antibodies in biological samples such as serum and urine. When reacting the solid phase and the liquid phase, it is customary to employ a labeled antibody as a reagent and to measure the liquid phase after the reaction by using a detector. Known examples of the label are a radioisotope, an enzyme, a colored particle, a fluorescent material, a luminescent material, etc.
Japanese patent laid-open Hei-3-46565 teaches enzyme immunoassay which is performed by using magnetic particles coated with a polymer having a reactive radical. The absorbance or the fluorescent intensity of the liquid phase is measured in this prior art.
WO 87/06706 teaches, as label agents, many examples of materials emitting a chemiluminescence and materials emitting an electro-chemiluminescence. It is suggested that, of those materials, an organic compound of ruthenium or osmium is preferable as a label for the electro-chemiluminescence. This prior art also teaches that, after an immunoreaction is progressed using magnetic particles as the solid phase, the solid phase is magnetically separated from the liquid phase and an electro-chemiluminescence is measured for the liquid phase. Such a process of separating the bound component and the free component is called B/F separation.
While the above two prior arts measure the liquid phase, U.S. Pat. No. 4,141,687 teaches it to measure a label on the solid phase. More specifically, in U.S. Pat. No. 4,141,687, magnetically attractable particles are used as the solid phase, a radioactive atom is used as the label, and an immunoreaction is progressed in a flow path. After the immunoreaction, a reaction mixture is introduced to flow through a magnetic trap. At this time, the liquid phase passes through the magnetic trap, but the solid phase is held in the trap. After washing, the solid phase is released from the magnetic trap and then introduced along a conduit to pass through a downstream coil, followed by measurement of its radioactivity by a scintillation counter.